Recently, a device for digital recording and/or reproduction of music data, such as CD (Compact Disc) or a MD (Mini Disc), is in widespread use. As a result, it has become possible with relative ease to make illicit duplication of digital music data, by employing the device for digital recording and/or reproduction of music data in combination with e.g., a personal computer. Thus, a variety of methods have been proposed to prevent such illicit duplication of music data as a copyright protected work.
For example, it has been proposed that reciprocal authentication be made between the copying source and a device of the copying destination, under control by the software controlling the copying source, and that, if proper results of authentication are acquired, music data is encrypted to the device of the copying destination, which then decodes and uses the encrypted data.
It has also been proposed that reciprocal authentication be made between the copying source and a device of the copying destination with the aid of the identification information stored in a pre-set hardware.
It has likewise been proposed to execute the authentication, encryption and decoding by the hardware of the hard-wired logic.
However, if the authentication, encryption and decoding are executed solely with the software, there is a risk that the software be analyzed and modified to make illicit duplication of music data.
Also, if the pre-set ID is stored on the hardware so as to be read by the software on the personal computer and used, there is a risk that the ID thus read out be read out, analyzed and modified in the course of its transmission to the software.
Moreover, if the authentication, encryption and decoding are executed by the hardware of the wired logic, it is possible to prevent analysis and modification, however, if authentication, encryption and decoding are to be made anew, it is necessary to exchange the existing hardware with a new hardware or to add a new hardware.